Most social media sites consequently use the nofollow attribute, and this would mean that the traditional approach to ranking pages is not an initiator. Of course, there are those who believe that Google is selective in the sense of treating nofollow links.
One should keep in mind that the signal is not always the same as the ranking factor. Google said: “We are using it as a signal in ranking of organic news and results. Also, we use it for improving news on the basis of how many people shared an article.”
Other types of signals are:
- The concept of trust (sites and users)
- Temporal (speed)
- Context (semantics)
Via Antonino Militello